ACE 2021

Question 1

What is the OPTIMAL depth of the ETT (read from the skin surface of the tracheostomy) to ensure the tip of the ETT is safely positioned?

Answer 1

5-6 cm

For patients with mature tracheostomies who are having further head and neck procedures, it is advantageous to remove the existing tracheostomy tube and insert a wire-reinforced endotracheal tube (ETT) through the stoma, pulling it back after placement until the top of the ETT cuff can be visualized. Placement of an ETT through a mature tracheostomy should not extend past 5 to 6 cm to avoid risking carinal irritation or endobronchial intubation

Question 2

Which intravenous medications is MOST appropriate for the management of acute pulmonary hypertension?

Answer 2

Epoprostenol

Question 3

During performance of an ultrasound-guided popliteal block, the following image is obtained. What is MOST likely indicated by the arrow?

Answer 3

A bayonet artifact

Question 4

What can you say about reverberation artifact on ultrasound image?

Answer 4

Reverberation artifact, detailed in a stepwise manner. Each number above the needle (top) has a corresponding number on the ultrasound screen (bottom) to graphically represent the result of different reverberation events. The original ultrasound beam contacts the needle and is reflected back to the probe correctly (1). In addition, part of the ultrasound beam penetrates the hollow needle and is reflected back to the probe from the distal wall of the needle (2). However, a component of the ultrasound beam becomes “stuck” within the needle lumen because the needle walls are highly reflective barriers. This signal component is reflected between the needle walls several times before “escaping” back to the probe (3), (4). Thus, the probe interprets these later occurring signals as objects distal to the needle at intervals which are multiples of the needle diameter.

Question 5

Which of the factors is MOST likely to be associated with significant bradycardia when traction is applied to an extraocular muscle?

Answer 5

The oculocardiac reflex has been well described for more than 100 years. It is more common in younger patients, and tends to lessen with age. The traction on an extraocular muscle is most likely to activate the reflex, but direct pressure on the eye, either externally or from a retrobulbar injection, is also known to cause the reflex. The most common symptom of the oculocardiac reflex is sinus bradycardia, but atrioventricular block and even asystole have been described. In the intraoperative setting, the most effective intervention to correct a dysrhythmia associated with the oculocardiac reflex is to remove the inciting cause (eg, release traction on the extraocular muscle), which usually restores heart rate within 20 seconds. Prophylaxis to prevent the oculocardiac reflex remains a somewhat controversial topic. Retrobulbar block with local anesthetic is highly effective in preventing the reflex, but pressure from the injection has been known to trigger it. Chemoprophylaxis with an antimuscarinic agent is not routinely recommended for adults. In children, there are some practitioners who advocate antimuscarinic pretreatment of all children undergoing eye muscle surgery. For surgery performed on eye muscles with general anesthesia, there are several factors that are thought to modify the risk of triggering the oculocardiac reflex. HYPERCARBIA and HYPOXIA are both known to increase the likelihood of developing the oculocardiac reflex. Choice of anesthetic also plays a role, with propofol-based anesthetics having the HIGHEST incidence of bradycardia, ketamine-based anesthetics having the LEAST, and volatile-based anesthetics falling in between. The use of remifentanil has also been shown to increase the risk of bradycardia in those undergoing eye muscle surgery.

Question 6

A 23-year-old woman presents for emergent surgery after sustaining an open femur fracture in a motor vehicle collision. She admits to using crack cocaine regularly, most recently just prior to the accident. Intraoperatively, electrocardiographic changes consistent with myocardial ischemia are noted. Her blood pressure is 185/95 mm Hg and her heart rate is 122/min. What is the MOST appropriate medication to administer?

Answer 6

NICARDIPINE

Cocaine inhibits presynaptic uptake of neurotransmitters, including norepinephrine, epinephrine, dopamine, and serotonin. This increases the availability of these neurotransmitters. Cocaine also acts as a local anesthetic by blocking cell membrane sodium channels. Initial myocardial ischemia management includes oxygen, aspirin, benzodiazepines, and nitroglycerin. Nicardipine is an appropriate choice for the treatment of hypertension in this scenario.

Sodium nitroprusside may lead to hypotension and reflex tachycardia and should be avoided.

Metoprolol and other β blockers may worsen coronary vasoconstriction secondary to unopposed α-adrenergic effects and thereby worsen ischemia.

Question 7

Why give stress dose steroids to patients on chronic steroid therapy? How much would you give?

Answer 7

To prevent cardiovascular collapse!

Cortisol is a hormone that is responsible for controlling a constellation of critical physiologic functions, including β-receptor synthesis, thus regulating cardiac output, contractility, vascular tone, and catecholamine sensitivity. Because of cortisol’s crucial role in cardiovascular homeostasis, a person without adequate amounts of cortisol can develop potentially fatal cardiovascular collapse. Cortisol also stimulates gluconeogenesis, and activates antistress and anti-inflammatory pathways. Cortisol production is self-regulated by negative feedback loops that control the release of CRH and ACTH. Exogenous administration of steroids will suppress the normal production of steroids, resulting in secondary adrenal insufficiency. Under normal conditions, the human body produces about 10 mg of cortisol every day. Under mildly stressful conditions (minor surgery), cortisol production may rise to 50 mg per day. Under extremely stressful conditions (major surgery), cortisol production may rise to 150 to 200 mg daily. Chronic steroid therapy has been associated with an increased risk of perioperative adrenal insufficiency. It is generally recommended to administer a stress dose of steroids to avoid the rare, but potentially fatal, complications of secondary adrenal insufficiency

Question 8

After cesarean delivery, a newborn male is noted to be diffusely cyanotic, with a heart rate of 50/min and a weak cry and facial grimace when vigorously stimulated. He has floppy muscle tone and slow, weak respiratory efforts. What Apgar score is MOST appropriate for this neonate?

Answer 8

3

The Apgar scoring system is useful in that it can be assessed while care is being provided for the newborn. A score between 7 and 10 is considered reassuring, scores from 4 to 6 are considered moderately abnormal, and scores of 3 or below are very concerning and typically associated with a poor outcome.

The neonate in the scenario would receive 3 points out of 10 as follows: Appearance (skin color diffusely cyanotic): 0 points Pulse (50/min): 1 point Grimace (weak cry and facial grimace when stimulated): 1 point Activity (floppy muscle tone): 0 points Respiration (slow): 1 pointThis score is very low and would be of great concern.

Question 9

List patient-related risk factors for the development of postoperative neuropathies?

Answer 9

Peripheral nerve injuries can manifest after patients undergo surgery. Although neuropathies can result from improper intraoperative patient positioning, they can also occur despite appropriate anesthesia care (eg, during intubation or performance of regional anesthetic techniques). Thus, preventive measures may not be effective for all patients.

According to the American Society of Anesthesiologists practice advisory on this topic, a focused preoperative history may identify patients with increased risk for the development of postoperative peripheral neuropathies. These patient-related risk factors include:

• Male sex
• Extremes of weight
• Preexisting neurologic symptoms
• Diabetes mellitus
• Peripheral vascular disease
• Alcohol dependence
• Tobacco use
• Arthritis

Question 10

Which of the following conditions is MOST likely associated with upregulation of nicotinic acetylcholine receptors? Downregulation? Why is it important?

Answer 10

Physiologic states that influence the expression of nicotinic acetylcholine receptors at the neuromuscular junction and along muscle membranes can influence the response to both depolarizing and nondepolarizing neuromuscular blocking drugs. Upregulation of nicotinic acetylcholine receptors occurs in a variety of conditions. This is typically associated with a relative resistance to nondepolarizing neuromuscular blocking drugs. Upregulation and proliferation of postjunctional acetylcholine receptors is associated with increased sensitivity to succinylcholine, and can lead to massive—and fatal—release of intracellular potassium when succinylcholine is administered. This condition is well known in patients with spinal cord injury and burns, but can occur even without a denervating injury in hospitalized patients with prolonged immobility.

Question 11

Metformin is MOST likely associated with which of the following metabolic abnormalities?

Answer 11

lactic acidosis

Metformin is generally accepted as a first-line treatment for type 2 diabetes, and is currently the most commonly used oral agent for this condition. Several mechanisms have been proposed to explain the hypoglycemic effects of metformin. The primary mechanism seems to be reduction of gluconeogenesis, blunting the effects of glucagon and limiting the conversion of lactate and glycerol to glucose. Metformin has little effect on glucose levels in normoglycemic individuals.

Metformin is associated with severe lactic acidosis. Patients with liver dysfunction and those who are dehydrated, in heart failure, septic, or suffering from acute kidney injury are particularly at risk for this complication. Patients presenting with metformin-associated lactic acidosis may not look particularly sick, despite having significantly elevated serum lactate levels (>10 mmol/L). There is no specific treatment for metformin-induced lactic acidosis except withdrawal of the drug, gentle rehydration, and patience. Metformin should be stopped when patients are NPO and should not be taken on the morning of surgery.

Question 12

What is the MOST common cause of pregnancy-related deaths in the United States?

Answer 12

Cardiac disease

Recent studies indicate that, while mortality rates from historically reported obstetric causes have declined (eg, obstetric hemorrhage, preeclampsia, thromboembolism), deaths from cardiovascular conditions are increasing (eg, cardiomyopathy, cerebrovascular accidents).

A current study has reported that cardiac disease is responsible for over one-third (34%) of all pregnancy-related deaths, making it the most common cause of pregnancy-related death in the United States. It has been reported that an increasing number of pregnant women in the United States now suffer from preexisting chronic health diseases during pregnancy, including obesity, hypertension, and diabetes. Adverse effects of these diseases exacerbate the physiological cardiovascular changes of pregnancy, thereby placing the parturients at increased risk.

Question 13

What is the mechanism for the analgesic effects of intravenous magnesium sulfate?

Answer 13

(NMDA) receptor antagonism

Question 14

Should nonsteroidal anti-inflammatory drugs (NSAIDs) such as ketorolac be given to a hypovolemic patient?

Answer 14

NO

Nonsteroidal anti-inflammatory drugs (NSAIDs) such as ketorolac can cause acute kidney injury (AKI) by reducing renal blood flow. Renal blood flow is regulated by controlling the vasopressor state of the glomerular afferent and efferent arterioles within the kidney. In the setting of hypovolemia, arterial pressure falls along with renal perfusion pressure. Compensatory angiotensin release causes a general increase in blood pressure as well as constriction of the efferent arteriole of the glomerulus. This shifts the glomerular filtration curve toward higher blood pressures. Prostaglandin synthesis within the kidney causes the afferent arteriole of the glomerulus to preferentially dilate more than the efferent arteriole. Resistance that is higher in the efferent arteriole than in the afferent arteriole serves to maintain GFR within the autoregulatory range. NSAIDS reduce GFR because of loss of vasodilatory prostaglandin.

Persistent reduction in renal perfusion pressure below the autoregulatory range ( ie intraoperatively with protracted systemic hypotension or severe hypovolemia caused by hemorrhage and blood loss). In this state, endogenous vasoconstrictors released from the renal sympathetic nerves increase the afferent arteriolar resistance, which results in a rapid decline in GFR and a decrease in renal blood flow. This eventually leads to tubular cell damage and cell death.

Question 15

Promethazine for PONV?

Answer 15

BEST TO AVOID

There are several case reports of severe ischemic injury to the extremity, especially the affected hand, secondary to injection of promethazine into an intravenous (IV) catheter. If the medication is injected into an IV catheter that is not in a vein, it can lead to vasospasm with resulting tissue damage, necrosis, or—in severe cases—the need for amputation. Some hospitals have banned the use of IV promethazine, allowing it to only be administered via a central venous catheter. Others have removed the drug completely from the formulary.

Question 16

Which medication is MOST likely indicated for the management of elevated ICP in a hemodynamically unstable patient?

Answer 16

Hypertonic saline

Pharmacologic agents commonly used to reduce intracranial pressure (ICP) include mannitol, hypertonic saline, barbiturates, propofol, and midazolam. With both mannitol and hypertonic saline, osmotic mechanisms reduce brain bulk. However, hypertonic saline is indicated in the hemodynamically unstable patient because it also stabilizes blood pressure, presumably because it does not induce a negative fluid balance. Administration of mannitol causes a profound osmotic diuresis requiring replacement using intravenous fluid therapy.

Question 17

What is the ratio of partial arterial oxygen tension to fractional inspired oxygen (Pao₂/Fio₂ or P/F ratio) is MOST consistent with a healthy patient breathing room air at sea level?

Answer 17

500

The ratio of partial arterial oxygen tension to fractional inspired oxygen (Pao₂/Fio₂ or P/F ratio) is used to help diagnose and guide the care of mechanically ventilated patients with lung injury. A person who is breathing room air (21% oxygen) at sea level will have a Pao₂ of approximately 100 mm Hg. This person’s P/F ratio will be 476 mm Hg (100/0.21).

By definition, a patient with acute lung injury (ALI) has a P/F ratio between 300 and 200 mm Hg, while a patient with acute respiratory distress syndrome (ARDS) has a P/F ratio of 200 mm Hg or less.

Question 18

What is the MOST reliable predictor of full reversal from neuromuscular blockade?

Answer 18

Quantitative measurement of at least 90% recovery of the train of four

A substantial body of scientific study and expert opinion show that the only means to reliably know if neuromuscular function has fully recovered in a medically paralyzed patient—ie, a measured train-of-four ratio of at least 0.9—is to use an objective monitor. Physical tests such as head lift and grip strength can be positive even with ratios as low as 0.6. Visual and tactile assessments of train of four are common in clinical practice, but are poorly correlated with objectively measured function.

Question 19

A 60-year-old patient is undergoing resection of a large pituitary mass. Postoperatively, secretion of which of the following hormones is MOST likely to be affected by this surgery?

Answer 19

Antidiuretic hormone (ADH)

The most common postoperative complication of pituitary surgery is the interruption of secretion of antidiuretic hormone (ADH). ADH is synthesized in the hypothalamus, then transported and stored in the posterior pituitary (also called the neurohypophysis). Its secretion from the posterior pituitary regulates water balance.

Question 20

Following spinal anesthesia for cesarean delivery, in which of the following situations should phenylephrine be AVOIDED for treatment of hypotension?

Answer 20

Maternal bradycardia

Hypotension is a common phenomenon after placement of spinal anesthesia for cesarean delivery. Preloading or coloading with intravenous fluid, either crystalloid or colloid, is often employed to reduce the degree and frequency of hypotension. Along with fluid boluses, vasopressors are also used routinely—preferably prophylactically—to treat hypotension. Phenylephrine and ephedrine are the 2 vasopressors predominantly used to treat spinal-induced hypotension during cesarean delivery. Phenylephrine is an α agonist that increases systemic vascular resistance, and is currently recommended as the initial choice for spinal-induced hypotension. Compared to intermittent bolus administration, a continuous infusion of phenylephrine started immediately after the placement of spinal anesthesia is reported to be superior for management of hypotensive episodes. As stated in recent obstetric anesthesia practice guidelines, in the absence of maternal bradycardia, phenylephrine should be considered as the primary vasopressor for treatment of spinal-induced hypotension due to the improved fetal acid–base status observed with uncomplicated pregnancies following its administration.

Question 21

A 50-year-old man scheduled for cerebral aneurysm clipping underwent a preoperative assessment for occasional left chest and arm discomfort. His exercise nuclear perfusion scan and coronary angiogram were normal. One hour after anesthetic induction, his intraoperative electrocardiogram abruptly changed while vital signs remained stable:

What treatment is MOST likely indicated?

Answer 21

Nitroglycerin

Coronary artery vasospasm (CAS) is a well-known entity during percutaneous coronary intervention, with an incidence of 18% to 20%. However, it is also clinically significant in the pathogenesis of variant angina, acute myocardial infarction (MI), and sudden death. Successful treatment of acute attacks has been reported using nitroglycerin or calcium channel antagonists.

Nonselective β blockers such as propranolol may be detrimental because β₂-receptor blockade prevents β₂-mediated vasodilation, allowing for unopposed α-receptor mediated coronary vasoconstriction, and may worsen ischemia. β Blockers and adrenergic agents such as epinephrine are reported to elicit CAS and are not likely to be a successful treatment.

Question 22

At what point during the perioperative period is a patient having noncardiac surgery MOST likely to experience myocardial infarction?

Answer 22

Within 72 hours of surgery

Most cases (75%–85%) of perioperative myocardial infarction (MI) occur within 72 hours after surgery. The highest risk of death after perioperative MI is reported to be during the first 48 hours. Almost 65% of patients with perioperative MI do not experience typical ischemic symptoms, such as chest, epigastric, or arm discomfort or pain, or shortness of breath. An absence of these symptoms has led to recommendations that troponin levels be monitored routinely in high-risk groups.

A strong association has been reported between intraoperative hypotension and myocardial injury and death. The risk of MI is reported to increase significantly when the minimum mean arterial pressure is less than 70 mm Hg for at least 10 minutes during surgery. The threshold for myocardial injury is noted to be a mean arterial pressure of 65 mm Hg. In a 2015 study, approximately 30% of hypotensive episodes with a mean arterial pressure below 65 mm Hg were recorded during the time between induction of anesthesia and surgical incision.

Question 23

For an adult undergoing general anesthesia, which of the following types of heat loss is the GREATEST contributor to a decrease in core body temperature?

Answer 23

Radiation

In an adult patient undergoing general anesthesia, there are 2 important reasons for a decrease in core body temperature: heat loss and heat redistribution. Heat loss that occurs in the operating room will always be due to at least 1 of the following: radiation, convection, evaporation, and conduction. Radiation of heat occurs with any object with a temperature above absolute zero (–273 °C). Radiation is the greatest contributor to a decrease in core body temperature in an adult undergoing general anesthesia, accounting for up to 60% of heat lost. Convection occurs whenever the thin layer of still air surrounding a patient becomes disturbed. After radiation, convection is the next most important cause of heat loss, accounting for approximately 30% of heat lost. Evaporation occurs from sweating, which is markedly impaired by general anesthesia (usually less than 10% of the total heat lost). Heat loss from conduction is proportional to the temperature difference between 2 objects and the degree of thermal insulation. In the operating room, patients are usually in direct contact with the foam or gel pads and are usually negligible.

In contrast to heat loss, redistribution represents the initial rapid phase of core body temperature decrease that occurs during the approximate first hour of general anesthesia. It does not represent heat loss per se, but rather heat redistribution. In the normal (nonanesthetized) state, core body temperature is not evenly distributed, with the periphery being approximately 2 to 4 °C cooler than the core. This gradient between the core and periphery is maintained by thermoregulatory vasoconstriction. Anesthesia impairs these thermoregulatory mechanisms and allows warm blood from the core to flow to the periphery, and cool blood to return to the core.

Question 24

A patient with a known difficult airway is being prepared for awake fiberoptic intubation. Several minutes after benzocaine is applied to the oropharynx, the patient develops cyanosis, tachycardia, and tachypnea. Administration of which of the following is the MOST appropriate next course of action?

Answer 24

Methylene blue

Benzocaine is an ester local anesthetic that is primarily used to provide topical anesthesia. When applied to the oropharynx, it has an onset of action that is usually within 60 seconds, and provides a duration of anesthesia of approximately 10 minutes. It is most commonly available as an aerosolized 20% solution, with an expulsion rate of approximately 200 mg/s. Due to the high expulsion rate of the drug in its aerosolized form, clinically significant methemoglobinemia can be induced with only a few seconds of application. While most local anesthetics can cause methemoglobinemia, benzocaine and prilocaine are the 2 agents most commonly implicated.

Normal methemoglobin levels are < 1%, and occur as the result of normal oxidative stress.

~ 5% - cyanosis, tachycardia, and tachypnea, which worsen as the level of methemoglobin increases.

~20% - ischemic electrocardiogram changes, chest pain, hypotension, and altered mental status.

As levels continue to rise, patients will become comatose.

~70% - death is likely.

The primary emergency treatment for symptomatic methemoglobinemia is methylene blue. An intravenous dose of 1 to 2 mg/kg resolves most cases, but this dose can be repeated if symptoms persist. Other modalities that can be considered if methylene blue fails or is contraindicated include hyperbaric oxygen and exchange transfusion.

Question 25

Currently, the use of ______ tubes rather than ______ tubes has become an accepted practice in infants and children.

Answer 25

Currently, the use of cuffed tubes rather than uncuffed tubes has become an accepted practice in infants and children. There are many advantages to using a cuffed versus uncuffed endotracheal tube:

Decreased number of intubation attempts to determine the correct size of endotracheal tube (in the 2009 trial, the tube exchange rate was 30.8% in the uncuffed group vs 2.1% in the cuffed group)

More accurate end-tidal carbon dioxide tracing

Better measurement of respiratory parameters of ventilators and end-tidal anesthetic level

Better ability to provide increased airway pressures in patients with restrictive lung disease

Decreased waste and cost of inhalation agents

Less operating room pollution from leaked gases

Potential to decrease risk of airway fire or microaspiration

Question 26

A patient requires emergent surgery for a retinal detachment. Two hours earlier, she vaped marijuana to treat anxiety, although she has not previously been a cannabis user. What is the MOST likely physiologic result of her acute cannabis intoxication?

Answer 26

Systolic hypertension

Question 27

You are starting an intravenous maintenance fluid for a child who weighs 25 kg. Using the method of Holliday and Segar, which of the following is the MOST appropriate administration rate?

Answer 27

65 ml/hr

the 4-2-1 rule: 4 mL/kg/h for a patient’s first 10 kg of weight, 2 mL/kg/h for a patient’s next 10 kg of weight, and 1 mL/kg/h for the remainder of the patient’s weight. For the 25-kg patient in the clinical scenario:

• The first 10 kg should receive 40 mL/h (10 kg × 4 mL/kg/h)
• The second 10 kg should receive 20 mL/h (10 kg × 2 mL/kg/h)
• The remaining 5 kg should receive 5 mL/h (5 kg × 1 mL/kg/h)

Thus, the estimated maintenance fluid rate for a 25-kg patient will be 65 mL/h.

Question 28

Active body surface warming during surgical procedures was shown to have the greatest effect on the reduction of surgical site infections

Answer 28

the reduction of surgical site infections

Major cardiovascular complications, patient comfort, shivering, and blood loss were all reduced to some extent.

Question 29

Which of the following drugs is MOST effective for reversal of the anticoagulation effects of dabigatran?

Answer 29

Idarucizumab

Idarucizumab, a monoclonal antibody fragment, binds to dabigatran and reverses its anticoagulant effect. It is approved by the US Food and Drug Administration to treat adults receiving dabigatran when rapid reversal of anticoagulation is needed for emergency procedures or in the presence of life-threatening bleeding.

Question 30

During emergence from a knee arthroscopy procedure using general anesthesia with a laryngeal mask airway, a 25-year-old, otherwise healthy woman develops laryngospasm requiring the administration of succinylcholine. An hour after the end of the case, she is in the recovery area, awake and alert, but requiring nasal cannula oxygen at 3 L/min to maintain an oxygen saturation of 94%. She has a cough productive of frothy sputum. What is the MOST likely etiology of her continued need for supplemental oxygen?

Answer 30

Negative pressure pulmonary edema

Any mechanism that results in a patient making a forceful inspiratory effort against a closed glottis may cause postobstructive pulmonary edema. However, in the perioperative setting, laryngospasm is the most common cause. Young, healthy patients are felt to be at highest risk of developing postobstructive edema due to the increased negative intrathoracic pressure they are able to generate.

Management of postobstructive edema is mostly supportive and consists of monitoring and the administration of supplemental oxygen and diuretics. More severe cases may require noninvasive positive pressure ventilation, or, rarely, the need for reintubation and mechanical ventilation.

Question 31

Administration liposomal bupivacaine in conjunction with lidocaine for infiltration in the surgical wound? Good idea?

Answer 31

NO

It is common to mix plain and liposomal bupivacaine for field blocks of the shoulder, leg, or abdomen. However, when coadministered with any local anesthetic other than bupivacaine, the liposomal drug delivery system is disrupted, leading to a systemic increase in bupivacaine exposure. Liposomal bupivacaine administration should be delayed at least 20 minutes following the local administration of lidocaine in the same area. Similarly, contact of liposomal bupivacaine with either wet chlorhexidine or povidone iodine solutions can disrupt the liposomal system, causing an immediate and uncontrolled release of bupivacaine from liposomal vesicles and associated adverse effects. Topical antiseptics should dry completely prior to the administration of liposomal bupivacaine.

Coadministration with a spinal anesthetic is unlikely to pose a risk for toxicity, as the volume of spinal anesthetic administered is small and the intrathecal location of injection is partitioned from the bloodstream. The risk for local anesthetic toxicity in this setting is low.

Question 32

Which is the MOST common cause of acute liver failure in the United States?

Answer 32

Acetaminophen poisoning

There are an estimated 2,000 cases per year of ALF in the United States, with the most frequent cause being acetaminophen poisoning (Figure 1). While rapid treatment with N-acetylcysteine is an effective antidote for acetaminophen ingestion, it must be given early to be effective. In many such patients, especially those presenting in coma, the cause of ALF is often not identified early enough to contribute to a positive outcome. Less common causes of ALF include viral hepatitis, other drug reactions or intoxications, and preeclampsia. In most cases of fulminant hepatic failure, the only effective treatment will be hepatic transplantation. ALF patients are given very high priority for available organs, but many deteriorate and die before a donor organ becomes available.

Question 33

Which is the PRIMARY pharmacological effect of magnesium on the neuromuscular junction?

Answer 33

Inhibit release of acetylcholine from the presynaptic membrane

Magnesium, the second-most-common intracellular cation, plays a key role in many physiologic processes. High plasma magnesium concentrations cause neuromuscular weakness and have been shown to potentiate nondepolarizing neuromuscular blockers. It has been reported that the median effective dose of vecuronium is reduced by 25% with concomitant administration of magnesium. Magnesium also reduces the time of onset and prolongs the recovery time of neuromuscular blockers.

The neuromuscular blocking activity of magnesium is primarily effected through the inhibition of calcium-mediated release of acetylcholine from the presynaptic membrane.

Question 34

A week after thyroid resection, a patient complains of difficulty speaking in a higher pitch. Which of the following nerves was MOST likely injured during surgery?

Answer 34

Superior laryngeal

The larynx is innervated mainly by the recurrent laryngeal nerve (RLN) and the internal and external branches of the superior laryngeal nerve (SLN). The RLN provides motor innervation to most of the laryngeal musculature, except the cricothyroid muscle, which is innervated by the external branch of the SLN.

RLN injury occurs in about 2.5% to 5% of thyroid surgeries and may be permanent in 1% to 1.5% of occurrences. Injury may occur due to traction on the RLN during surgery. With unilateral RLN injury, the vocal cord may assume a paramedian position, which can lead to hoarseness and difficulty with vocalization. Bilateral RLN injury can result in immediate stridor and dyspnea after extubation requiring reintubation.

Injury to the external branch of the SLN is less frequently reported than RLN injury, and results in dysfunction of the cricothyroid muscle. Patients may report difficulty reaching higher pitches or speaking loudly. Visualization during surgery may lead to a lower incidence of injury.

Question 35

List some of the things to keep in mind while caring for patient with MS

Answer 35

The stressors associated with surgery or childbirth are known triggers for exacerbation of MS symptoms.

In addition, increases in body temperature (by as little as 1 °C) are known to trigger exacerbations of symptoms. It is thought that increased body temperature causes reduced effectiveness of conduction in demyelinated nerves.

Spinal anesthesia with local anesthetics has also been implicated in exacerbating MS symptoms. (epidural anesthesia is thought to be safer due to the lower concentration of local anesthetic in the white matter).

The use of succinylcholine* in patients with MS, complicated by *profound motor weakness*, could result in an *exaggerated release of potassium.

The response to nondepolarizing muscle relaxants can vary from exaggerated responses to resistance.

Question 36

A review of your patient’s medical history indicates that she is a CYP2D6 poor metabolizer. Which of the following opioids would be MOST appropriate for this patient?

Answer 36

Hydromorphone, morphine, and oxymorphone are not metabolized through CYP2D6 and would be more likely to provide adequate analgesia in CYP2D6 poor metabolizers.

Patients who are known to be CYP2D6 poor metabolizers may experience ineffective analgesia when administered opioids that rely on this enzyme. For example, codeine is a prodrug that is converted to its active metabolite (morphine) by CYP2D6. In a CYP2D6 poor metabolizer, codeine may have decreased metabolism and decreased analgesic effects. Tramadol is a synthetic opioid that also relies on CYP2D6 to convert tramadol to O-desmethyltramadol, which is its most effective analgesic metabolite. In a CYP2D6 poor metabolizer, tramadol may have decreased metabolism and decreased analgesic effects.

Question 37

A 75-year-old woman presents for emergent evacuation of a postoperative hematoma of the left breast. Her medical history is significant for hypertension, diabetes, ischemic cardiomyopathy, and an implantable cardioverter defibrillator (ICD), which you can palpate below her left clavicle. Her most recent electrocardiogram is presented below:

Which of the following perioperative management strategies is MOST appropriate for this patient?

Answer 37

Reprogram the ICD (NOT place magnet over ICD intraoperatively!)

Based on her history, the device is an (ICD), and the ECG presented shows a pacer spike before every QRS. It is highly likely that this patient, while requiring anti-tachyarrhythmia therapy, also may be dependent on the device’s pacemaker function. Placing a magnet over most ICDs will inhibit the delivery of tachyarrhythmia therapy, but will never affect the pacemaker function. Because the surgical field is in proximity to the device, there is an increased risk of EMI. If the device senses electrosurgical EMI and interprets it as an intrinsic cardiac electrical impulse, pacemaker function may be inhibited, causing the patient to exhibit bradycardia or asystole.

It is generally recommended that, if a patient has an ICD, is pacemaker dependent, and there is a significant risk of EMI (particularly if the surgical field is close to the device as in the clinical scenario), the device should be reprogrammed. This commonly involves suspending the tachyarrhythmia therapy and setting the pacemaker to some type of asynchronous mode that is appropriate and safe for the patient.

After the procedure is complete, it is imperative to return the device to its previous settings.

Question 38

What can you say about perioperative atrial fibrillation (POAF)

Answer 38

Perioperative atrial fibrillation (POAF) is common and associated with increased in-hospital morbidity and mortality rates, increased lengths of stay, and higher costs. New-onset atrial fibrillation has also been reported to be an independent predictor for stroke. POAF rates from 2% to 60% have been reported, depending on the type of surgery. There is a strong correlation with age, with older patients being at higher risk. Both patient and surgical factors play a role in the development of POAF. Reversible causes of POAF include perioperative hypoxemia, hypercapnia, fluid overload, acidemia, and increased catecholamine levels (both endogenously and exogenously). The infusion of noncatecholamine vasoactive drugs such as phenylephrine is associated with a lower risk of POAF compared to the infusion of catecholamines. Some reports describe an occurrence of 4.8% with total joint arthroplasty and 12% to 19% with esophageal, thoracic, or abdominal surgery.

Electrolyte abnormalities are associated with an increased risk of POAF. However, hypOkalemia and hypOmagnesemia, rather than hyperkalemia, are the electrolyte abnormalities most commonly associated with POAF.

Question 39

What BEST describes the mechanism of action of tranexamic acid (TXA)?

Answer 39

It inhibits the transformation of plasminogen to plasmin

This decreases the conversion of plasminogen to plasmin, preventing fibrin degradation and preserving the framework of fibrin’s matrix structure. TXA has been consistently shown to reduce red blood cell transfusion in cardiac surgery, trauma, and hip and knee arthroplasty, where it has become the standard of care. The 2015 American Society of Anesthesiologists (ASA) practice guidelines for perioperative blood management support the use of perioperative TXA to reduce transfusion for patients at increased risk for bleeding. There is a low-level risk of thrombotic events; therefore, TXA is typically avoided in patients who have preexisting thromboembolic disease.

Question 40

A 45-year-old man presents preoperatively for evaluation. His medical history reveals a recent diagnosis of hyperaldosteronism with hypertension (Conn syndrome) as a result of an adrenal adenoma. Which laboratory abnormalities is MOST likely in this patient?

Answer 40

Hypokalemia, metabolic ALKAlosis

Primary hyperaldosteronism, commonly known as Conn syndrome, is usually caused by bilateral adrenal hyperplasia (60%) or a unilateral adrenal adenoma (40%). Patients with hyperaldosteronism typically exhibit a hypokalemic metabolic alkalosis, hypertension, and muscle weakness. Aldosterone regulates many functions through the renin–angiotensin–aldosterone system. Hyperaldosteronism leads to increased potassium excretion and hypokalemia. In addition, the overproduction of aldosterone results in hypertension from sodium and water retention.

Secondary hyperaldosteronism results from another disease process, such as cirrhosis with ascites or congestive heart failure. These disease states can result in low circulating intravascular volume, triggering the release of excess aldosterone via the renin–angiotensin–aldosterone system.

Question 41

Which is MOST likely to occur in a chronic smoker who quits smoking tobacco 48 hours prior to surgery?

Answer 41

Decrease in carboxyhemoglobin level

Smokers have a higher risk of death and surgical site infection, as well as cardiac and pulmonary complications. In systematic reviews, decreases in pulmonary complications were demonstrated only when preoperative smoking cessation occurred at least 4 weeks before surgery. Preoperative smoking cessation at least 2 weeks before surgery has been associated with a decrease in complications related to wound healing.

Smoking cessation for 48 hours has been shown to decrease carboxyhemoglobin levels (from 6.5% to 1%) and shift the oxyhemoglobin dissociation curve to the right (the PaO₂ at which hemoglobin is 50% saturated increases from 22.9 to 26.4 mm Hg within 12 hours of cessation). It also decreases cyanide levels, which benefits mitochondrial oxidative metabolism. Lower nicotine levels improve vasodilation and clearance of many toxic substances that may impair wound healing.

Question 42

Postpartum neuropathies MOST commonly involve injury to which peripheral nerve?

Answer 42

lateral femoral cutaneous nerve

Compression of the lateral femoral cutaneous nerve, a purely sensory nerve, is the most commonly reported injury in patients with postpartum obstetric neuropathy. The clinical condition, also known as meralgia paraesthetica, results from entrapment and compression of the lateral femoral cutaneous nerve between the anterior superior iliac spine and the inguinal ligament. Sensory abnormalities such as numbness, tingling, and burning are the most common symptoms of this condition, often misdiagnosed as a complication of neuraxial anesthesia.

Injury to the femoral nerve is the second-most-common neurologic deficit in the postpartum period. The inguinal ligament may compress the femoral nerve at the site of its passage underneath the ligament. The femoral nerve may also be compromised within the pelvis due to compression by the fetal head. A sign of femoral nerve injury is weakness of the quadriceps muscle.

Question 43

Hypophosphatemia is MOST likely to be associated with which condition?

Answer 43

Refeeding syndrome

Patients with hypophosphatemia become symptomatic as phosphorus falls below 1.0 mg/dL. At such levels, intracellular phosphate depletion causes impaired energy metabolism, resulting in significant cellular dysfunction. Severe hypophosphatemia decreases 2,3-diphosphoglyceric acid (DPG), which increases hemoglobin’s affinity for oxygen, decreasing oxygen delivery to the tissues. Central nervous system symptoms include weakness, tremors, and paresthesia. Progressive hypophosphatemia can lead to delirium, seizures, central pontine myelinolysis, coma, and death. The function of both smooth and skeletal muscle can be affected due to decreased adenosine triphosphate in hypophosphatemia. This can present as proximal muscle weakness, ileus, cardiomyopathy, and respiratory failure. The most severe cases of hypophosphatemia due to transcellular redistribution are associated with refeeding syndrome (enteral and parenteral nutrition). Starvation causes total body depletion of phosphorus; however, serum phosphorus is typically maintained. With refeeding, increased insulin secretion promotes phosphorus uptake into cells where it is consumed. ⅓ of ICU patients experienced refeeding-associated hypophosphatemia after being NPO for as little as 48 hours.

Ninety percent of the serum phosphorus is filtered at the glomerulus and 75% to 99% is reabsorbed. Renal failure causes hyperphosphatemia. Most of the phosphorus in the body is intracellular. Rhabdomyolysis causes release of intracellular phosphorus, leading to hyperphosphatemia.

Question 44

Shortly after induction of general anesthesia, a patient becomes profoundly hypotensive, peak airway pressure increases, and the patient develops urticaria. Which drug is MOST likely responsible for this reaction?

Answer 44

Rocuronium

Anaphylaxis is an immunoglobulin E (IgE)–mediated hypersensitivity reaction that results from mast cell and basophil activation. Upon initial exposure to an antigen, IgE is produced and binds to mast cells and basophils. Upon reexposure, the antigen cross-links 2 IgE receptors (bound to mast cells and basophils), which leads to release of preformed mediators. These mediators include histamine, proteases, proteoglycans, and platelet-activating factor, and result in cardiovascular collapse, bronchospasm, and urticarial rash.

Even though a great number of anesthetic drugs have been associated with anaphylactic reactions, muscle relaxants have been reported to be the most common offender (Table 1). Muscle relaxants may be responsible for up to 69% of anaphylactic reactions perioperatively, while hypnotic agents and opioids are estimated to be responsible for 3.9% and 1.4% of anaphylactic reactions, respectively.

Question 45

A patient’s trachea is extubated after a total thyroidectomy. Which symptoms would MOST likely indicate bilateral vocal cord paralysis?

Answer 45

Inspiratory stridor

The recurrent laryngeal nerves (RLNs) travel adjacent to the thyroid gland in the neck and supply motor innervation to the intrinsic muscles of the larynx, except the cricothyroid muscle. The cricothyroid muscle is the adductor of the laryngeal folds and is innervated by the superior laryngeal nerve. Injury to an RLN leads to unopposed adduction of the ipsilateral vocal cord. Bilateral vocal cord paralysis is characterized by inspiratory stridor due to the paramedian position of the vocal folds resulting from unopposed adduction by the cricothyroid muscles. Initial treatment may require emergent tracheostomy.

Dysphonia (hoarseness) is the most common complaint seen with unilateral vocal cord paralysis. Neoplasm is the most frequent etiology of unilateral vocal cord paralysis, with surgical injury being the second-most-common etiology. Dysphonia occurs due to the medialization of the paralyzed vocal cord.

Dysphagia is also a common complaint seen in unilateral vocal cord paralysis due to the inability of the vocal cords to come together in the midline during swallowing.

Question 46

Discuss American Society of Anesthesiologists practice advisory on perioperative visual loss associated with spine surgery?

Answer 46

Patients undergoing prolonged spine procedures—especially those in the prone position (>6.5 hours) or those involving excessive blood loss (>45% of the patient’s estimated blood volume)—are at increased risk for developing POVL. Ischemic optic neuropathy (ION) is the leading cause of POVL, while central retinal artery occlusion from external pressure on the globe is another possible cause. The latest consensus statements:

Blood pressure management - Assess baseline BP and maintain arterial pressure at higher levels in hypertensive patients (deliberate hypotension in high-risk patients only when essential).

Management of blood loss and administration of fluids - Use transfusions as deemed appropriate. Crystalloids or colloids alone or in combination may be used to maintain adequate replacement of intravascular volume. The incorporation of colloids may be associated with a decreased risk of POVL. Use of vasopressors - Vasopressors should be considered on a case-by-case basis when needed to correct hypotension.

Positioning - Position the patient’s head in a neutral forward position (without significant neck flexion, extension, lateral flexion, or rotation), either level or slightly above the body. Avoid direct eye compression (to prevent retinal artery occlusion) and check the eyes periodically. The use of a Wilson frame may be associated with increased risk of POVL.

Staging - may be considered on a case-by-case basis for high-risk patients. Breaking into 2 shorter stages may reduce the risk of visual loss.

Patient factors - Male sex and obesity have been associated with a higher risk for POVL caused by ION.

Question 47

A 29-year-old gravida 1, para 1 woman presents with right lower extremity weakness 3 days after an uneventful vaginal delivery with epidural analgesia. Physical examination reveals decreased strength of right hip flexion and knee extension, a diminished right patellar deep tendon reflex, and decreased sensation to cold and light touch over the right anteromedial thigh and calf. Which nerve has MOST likely been injured?

Answer 47

Femoral nerve

Femoral nerve injury manifests as weakness in hip flexion and knee extension, diminished patellar deep tendon reflex, and sensory loss over the anteromedial thigh and calf. Tenderness over the inguinal ligament and weakness of the iliopsoas and quadriceps femoris muscles indicate femoral nerve injury. The condition is bilateral in 25% of postpartum femoral neuropathies. Patients report difficulty climbing stairs or rising from a seated position. Compression of the femoral nerve under the inguinal ligament can be caused by abdominal distention, a large fetus, instrumental vaginal delivery, or lithotomy positioning associated with a prolonged second stage of labor. Femoral neuropathy can also result from intrapelvic pathology or retroperitoneal hemorrhage.

Question 48

Which of the drugs used in the treatment of asthma exhibits BOTH anti-inflammatory and bronchodilator effects?

Answer 48

Aminophylline

Within the lung, the parasympathetic nervous system controls airway caliber, glandular secretory function, and microvascular tone. The vagus nerve provides preganglionic innervation and the predominant neurotransmitter at the muscarinic postganglionic fibers is acetylcholine. β₂-Adrenergic agonists act directly on bronchial musculature as bronchial dilators. Anticholinergic drugs and adrenergic agonists can be administered systemically or directly via the pulmonary system. They exert their effects by altering the autonomic nervous system’s regulation of bronchomotor tone or glandular function, resulting in bronchodilation and decreased bronchopulmonary secretions. Aminophylline has both anti-inflammatory and bronchodilator activity. Historically a mainstay in the treatment of asthma, it is no longer considered first-line therapy due to its adverse effect profile and a subsequent need to monitor blood levels on a regular basis. However, it is still used when other treatments are ineffective or poorly tolerated.

The inflammatory process plays a significant role in both asthma and chronic obstructive pulmonary disease. There are many drugs, both systemically and directly administered, that are prescribed in the treatment of these diseases and specifically target the inflammatory component.

Question 49

A 62-year-old man taking isosorbide dinitrate for ischemic heart disease undergoes a transesophageal echocardiogram with topicalization using benzocaine spray. He is brought urgently to the operating room for management of esophageal perforation. After emergent induction, his pulse oximeter is reading 85% with an FIO₂ of 1.0. Arterial blood is obtained and noted to be chocolate brown. Which of the following is the MOST appropriate treatment?

Answer 49

Methylene blue

The clinical scenario indicates methemoglobinemia, the increased concentration of methemoglobin in the blood that occurs when hemoglobin undergoes oxidation. The ferrous (Fe²⁺) ions of heme are oxidized to ferric (Fe³⁺) ions. The ferric form of heme does not bind oxygen. This results in a leftward shift of the oxyhemoglobin dissociation curve and a decrease in oxygen delivery to the tissues.

Benzocaine is often used for topicalization in cardiac procedures and endoscopy, and excessive use can lead to methemoglobinemia. Administration of nitrites and nitrates can also lead to methemoglobinemia. Signs and symptoms may be seen at methemoglobin concentrations of 10% or higher. Oxygen saturation measured with standard pulse oximetry typically reads at 85%. Arterial blood gas will reveal an elevated PaO₂, but a PaO₂–oxygen saturation gap. Blood may appear dark or chocolate brown. Treatment for acquired methemoglobinemia is methylene blue, which reduces methemoglobin back to its unoxidized state. Ascorbic acid is an alternative treatment, especially in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency, as methylene blue may lead to hemolysis.